"A PROCESS FOR THE MANUFACTURE OF AN ALUMINIUM CONDUCTOR ALLOY WITH IMPROVED CONDUCTIVITY"

Abstract

The present invention relates to a process for the manufacture of an aluminium conductor alloy with improved electrical conductivity which is useful for electrical conductor applications. This alloy is prepared by minor alloying additions made into the base aluminium by various casting processes. The alloying additions enhance the electrical conductivity of the electrical grade and commercial grade aluminium. The alloy is prepared by the addition of 0.01 to 1% cerium, yttrium or misch metal and 0.005 to 0.2% Calcium to the base aluminium. These alloying additions enhances the electrical conductivity of the base aluminium by 0.5 to 2% I ACS (International Annealed Copper Standard).

Full Text

The present invention relates to a process for the manufacture of an aluminium conductor alloy with improved conductivity.
Aluminium has been in use for many years in such applications as electrical conductors due to its desirable combination of relatively high conductivity and low weight. The most popular form of aluminium for this purpose has been that formerly known as EC aluminium and now known by its Aluminium Association Registration No. 1350. Various other aluminium alloys have been formulated as replacement material for alloy 1350, such as 6201, 8001, stabiloy, triple, etc. Many high temperature resistance aluminium alloys have been developed making use of the elevation of recrystallisation temperature imparted by Zr compounds. A few of the alloys developed using rare earth or calcium are listed below :
i
As per the US patent No. US3615371 of 1968 Farukawa Electric Co. Ltd. has developed an all aluminium alloy conductor (AAC) with less than 0.6% of one or more of rare earth metal. The alloy is a ternary Al-Mg-RE alloy.
As per the British patent No. 1260307 of 1968, the British insulated Calendars' Cables Ltd. has developed 3 aluminium alloys containing rare earths. The first one contains 0.05-1% Cu, 0.1-1% Fe and 0.1-3% rare earth metals. The second one contains lesser amounts of alloying elements and are in the range 0.05-0.6% Cu, 0.1 - 0.1% Fe and 0.1 - 3% rare earths. The alloy may be cold worked at least 99%. The third alloy developed contains 0.5-0.8% Cu and together with 0.3-2% rare earth. The alloy is not cold worked more than 96%.
As per the Japanese patent No. 7329445 of 1968, Showa Electric Wire Cable Co. Ltd has developed two high strength, high thermal resistance all aluminium alloy conductor (AAC). The first alloy one contains 0.1-2.5% misch metal and the second additionally contains 0.2-0.6% Fe.

In 1970 Fuji Electric Co. Ltd. has patented in Japan, Patent No. 74-011283-1, a heat resistant all aluminium alloy conductor with 0.01-0.8% Mg, 0.01-0.8% Fe,0.001-0.3% B and 0.1-2.0 % rare earth metal.
Shin-Etsu has filed a Japanese patent No. 74099016 in 1972 for electric conductor material and which can be used as heating element. It consists of Al, 12.4%Y and 11.7% rare earth.
As per the Soviet patent 456845 of 1973, Goldbukht GE has developed an all aluminium alloy conductor containing the rare earth elements. The alloy contains 0.18-0.50% Fe, 0.05-0.15% Si, 0.001-0.10% Cu, 0.001-0.10% Zn, 0.001-0.08% B, 0.001-1.5% at least one of the rare earth metals viz., Ce, Dy, Y and La. They have also specified the impurity levels of the alloy. The total of Mn, Cr, V and Ti to be upto 0.015% and with total impurities not over 0.1%. The conductor had a UTS (ultimate tensile strength) of 193 to 208 MPa and elongation of 3.0 to 3.8%. This had a conductivity of 62.5 to 63.2% IACS.
Dainichi-Nippon Cables KK has patented in 1974 - patent No. J51071209, an aluminium alloy for indoor wiring. The alloy contains 0.26-0.8% Fe, 0.03% Cu, 0.3% of rare earths preferably misch metal and 0.005 to 0.08% Y. The alloy in the annealed and softened condition had an UTS of 120 to 130 MPa and 61% IACS conductivity. On hot working, the UTS increased to 230-260 MPa and the conductivity decreased to 58.5 to 60.1% IACS.
t
Dainichi Nippon Cables has developed a strong all aluminium alloy conductor as per the Japanese patent No. J51071209 of 1974. The alloy contains 0.25 to 0.5% Fe 0.1 to

0.2% Si, 0.03 to 0.3% Mg and 0.03 to 0.5% rare earth. This had a conductivity greater than 58% IACS and strength greater than 250 MPa.
Dainichi-Nippon Cables KK has developed a soft all aluminium alloy conductor as per the Japanese patent No. J51093713 of 1975. The alloy contains 0.6 to 0.15 Fe, 0,01-0.18% rare earth, 0.001 to 0.1% Y, 0.001 to 0.3% S and 0.01 to 0.3% Ca. The alloy had a conductivity greater than 60% IACS with UTS greater than 120 MPa and elongation greater than 12%.
Dainichi Nippon Cables Ltd. has developed a soft aluminium alloy as per the Japanese patent JAJ835254 of 1975. The alloy contains 0.6 to 1.5% Fe, 0.01 to 0.18 % rare earth, 0.001 to 0.1% Y, 0.01 to 0.3% S, 0.01 to 0.3% Ca and balance Al. The alloy had a conductivity greater than 60% IACS with strength greater than 120 MPa and elongation greater than 20%.
Southwire Co. has made a patent in 1976, patent No. US3964935, for an aluminium Cerium conductor alloy. It contains 0.55 to 1.2% Fe, 0.2 to 1.5% Ce, 0.15% each of Co. and Mg, in total not exceeding 0.25% and the combined amount of Fe and Ce ranging from 1.2 to 2.5%.
Furukawa Electric Co. Ltd has developed an all aluminium alloy conductor according to the Japanese patent No JAJ 8125950 of 1979. The alloy contains 0.01 to 0.5% Ti, 0.05 to 0.80 Fe at least one rare earth element in the range of 0.002 to 0.5%. They have also developed an alloy of high conductivity, high strength and heat resistance. This contains 0.02 to 0.08% Ti, 0.10 to 0.25% Fe and 0.05 to 0.3% rare earth metal.

Dainichi Nippon Cables has developed a non heat treatment type high conductivity aluminium in 1979, patent No. JAJ 8184440. The alloy had a composition of 0.25 to 0.5% Fe, 0.1 to 0.2% Si, 0.03 to 0.3% Mg, 0.03 to 0.5% rare earth and remaining Al. It had a strength greater than 250 MPa conductivity greater than 58% IACS.
According to a US patent No. 4213799 of 1980 by Swiss Aluminium Ltd., Chippis GHX, the electrical conductivity of aluminium has been improved through the addition of misch metal. They have developed an aluminium base conductor wire having an electrical conductivity equivalent to commercial grade aluminium conductor wire consisting essentially of 0.04 to 1.0% Fe, 0.02 to 0.2% Si, 0.1 to 1.0% Cu, 0.001 to 0.2% B, 0.001 to 1.0% rnisch metal, balance - aluminium
According to another US patent No. 4213800 of 1980 by the Swiss Aluminium Ltd. Chippis CHX, an electrical conductor aluminium has been developed through the addition yttrium.
According to the Japanese patent JP57-76175 of 1980 by Furukawa Denki Kogyo KK a manufacturing process has been developed for aluminium based setnihard electric wire. The alloy contains Fe, Mg, Cu, Zr and rare earth in the range of 0.005 to 1.0%, and the aluminium purity exceeding 99.65%.
Furukawa Denki Kogyo KK has a Japanese patent JP59-47365 of 1983 for production of aluminium alloy conductor having high strength and heat resistance. The aluminium alloy contains 0.15 to 0.8% Zn, 0.05 to 0.6% Fe, 0.04 to 0.20% Si and one or

more than one of the following elements, 0.005 - 0.5% Mg, 0.005 - 0.1% Cu, 0.01 to 0.5% rare earth elements, 0.0005 to 0.1% Sb, 0.005 to 0.1% Be and the balance Al.
Furukawa Electric Co. Ltd has developed an aluminium alloy through the Japanese patent JAJ 8447365A of 1983. The alloy contains 0.15 to 0.8% Zr, 0.05 to 0.6% Fe, 0.04 to 0.20% Si together with or without 0.005 to 0.5% Mg, 0.005 to 0.5% Cu and 0.01 to 0.5% rare earth and one or mre of 0.005 to 0.1% Sb and 0.005 to 0.1% Be.
None of these particular references teaches the alloy system contemplated by the present invention. The object of the present invention is top provide a method to enhance the electrical conductivity of the presently used electrical grade aluminium and the commercial grade aluminium.
Accordingly, the present invention provides a process for the manufacture of an aluminium conductor alloy with enhanced conductivity and comprising of
said process comprises preparing aluminium melt by heating aluminium and degassing successively by hexachloro ethane and dry nitrogen, adding 0.01 to 1 wt% rare earth metal selected from cerium, yttrium or misch metal and 0.005 to 0.2 wt% calcium, either in the elemental form or as master alloy, homogenizing , cooling and casting to obtain the desired alloy.

In an embodiment of the present invention, the aluminium used is commercial grade of 99% purity.
In another embodiment of the present invention, the aluminium melt is maintained at a temperature in the range of 740 to 800 ° C.
In yet another embodiment of the present invention, the degassing of the melt is effected using hexachloroethane and nitrogen.
In still another embodiment of the present invention, the rare earth and calcium used are commercial grade of 99 % purity.
The unique properties of the alloy of the present invention are achieved by adding Ce, Y or misch metal and Ca to the aluminium base alloy to enhance the conductivity. The addition of these alloying elements acts as a "scavenging agent" in the aluminium base to improve the conductivity.
The unique properties of the alloy of the present invention are achieved by the process of addition of cerium, yttrium or misch metal from 0.01 to 1% by weight together
with calcium from 0.005 to 0.2% by weight. The process could be modified to add yttrium or

misch metal instead of cerium to the same level. The base aluminium may contain 0.1 to 1% by weight iron, 0.05 to 0.5% by weight silicon, 0.001 to 0.1% by weight titanium, vanadium, copper and manganese upto 0.1% other impurities and the balance aluminium.
Alloys within these ranges to which cerium addition is particularly useful are those alloys containing 0.01 to 0.6% by weight iron and 0.01 to 0.5% by weight silicon. Aluminium generally contains small amounts of impurities originating either from the ore or from the process of extraction. Iron and silicon are the major impurities. Titanium, vanadium, zirconium and chromium, which go into solid solution with aluminium, may be present to small levels and seriously impair the electrical conductivity. They are generally precipitated out by the addition of boron to the levels of half of the above impurities. The present process utilises the addition of either cerium, yttrium or misch metal together with calcium to scavenge the major impurities like iron and silicon. The alloy may be cast in metal moulds or may be cast in conventional manner such as continuous cast. The cast billet or bars may be optionally homogenised at a temperature range of 300-500°C for 30 minutes to 2 hrs. The billet or bars homogenised or not, is deformed at elevated temperature in the range of 300 to 500°C. These deformed rods are annealed at between 300 to 450°C for 30 minutes to 6 hrs prior to cold drawing to the final wire form. The drawn wires may be further annealed to increase the electrical conductivity further but at the expense of strength.
The process and the alloy developed is illustrated by the following five examples and should not be constructed to limit the scope of the present invention.

(Table Removed)
The main advantages of the present invention are:
1. The strength of aluminium is enhanced without sacrificing the electrical conductivity.
2. The strength is improved by 10 to 20 Mpa.
3. Electrical conductivity is increased by 0.5 to 2% IACS.

We Claim:
A process for the manufacture of an aluminium conductor alloy with enhanced conductivity

said process comprises preparing aluminium melt by heating aluminium and degassing successively by hexachloro ethane and dry nitrogen, adding 0.01 to 1 wt% rare earth metal selected from cerium, yttrium or misch metal and 0.005 to 0.2 wt% calcium, either in the elemental form or as master alloy, homogenizing , cooling and casting to obtain the desired alloy.
A process as claimed in claim 1 , wherein the aluminium used is of grade greater than 99% purity.
A process as claimed in claims 1 and 2, the rare earth metal and calcium used is commercial grade of 99% purity.
4. A process for the manufacture of an aluminium conductor alloy with enhanced conductivity substantially described hereinbefore with reference to the examples contained therein.